package oo7;

public class USBTest {

	public static void main(String[] args) {

		System.out.println("USB的工作电压是" + USB.V);// Static
		// USB.V = 12;//报错，说明是final

		// USB u = new USB();
		USB u = new USBDisk();
		System.out.println(u);
		u.plugin();
		System.out.println(">>>>>>>>>>>>>");
		// 强制.可以用instanceof
		USBDisk ud = (USBDisk) u;
		ud.copyFile();

		u.unplug();

	}

}
